It is well recognized that proper and uniform spacing of seed in the furrow is essential to maximizing crop yield. The first step in achieving uniform spacing is to accurately dispense one seed and one seed only at the proper timing. This “singulation” accuracy is a performance benchmark that is well known for many types of seed meters, whether mechanical or pneumatic, and is often tested on a seed meter test stand prior to the beginning of the planting season.
There are many different manufacturers of pneumatic seed meters which fall into the more specific categories of air meters and vacuum meters. An example of one type of commercially successful air meter is disclosed in U.S. Pat. No. 3,888,387 to Deckler. An example of one type of commercially successful vacuum meter is disclosed in U.S. Pat. No. 5,170,909 to Lundie et al. Other commercially successful vacuum meters include those disclosed in U.S. Pat. No. 5,842,428 to Stufflebeam et al., U.S. Patent Publication No. 20050204972 to Eben et al., and U.S. Pat. No. 3,990,606 to Gugenhan. Many of these meters have historically operated at performance levels of 93% to 97% accuracy. Recent improvements to vacuum meters have allowed them to operate at a typical accuracy of 98 to 99%. The vacuum meter is capable of 99% singulation on some seed types but has been plagued with the need for adjustment in order to attain that performance. Secondly, the particular design of many of these meters has made them susceptible to reduced performance levels as a result of manufacturing tolerances.
A problem affecting singulation accuracy with vacuum meters that utilize “celled-disks” (i.e., disks with indentations or “cells” around each aperture in the disk, such as the disks disclosed in U.S. Pat. No. 5,170,909 to Lundie et al.), is that such meters have a higher tendency to plant “skips” and “doubles” in near succession when planting flat shaped seeds. Despite this tendency, however, celled-disk vacuum meters offer the unique advantage of permitting the meter to generally operate at lower vacuum levels than meters that use flat or non-celled disks (i.e., vacuum disks with apertures only) because the indentations or cells assist in holding the seeds in place, thus requiring less vacuum pressure to entrain the seeds.
In an attempt to improve singulation accuracy, farmers have tried to use non-celled disks with meters originally designed for celled-disk meters. For example, with the John Deere MaxEmerge vacuum meters, farmers started using one of the specialty disks designed by John Deere for planting irregular seeds such as sweet corn (thus, this disk is often referred to as the “sweet corn disk”). The sweet corn disk is flat on the planting surface and does not have any indentations or cells to hold the seed. Similar to the sweet corn disk, an update kit, known as the Accu-Vac Update Kit, available from S.I. Distributing, Inc. St. Marys, Ohio, utilizes a flat, non-celled disk. The Accu-Vac disk has larger apertures in order to ensure the seeds are adequately entrained so they do not prematurely slough-off as the disk rotates. While the sweet corn disk and the Accu-Vac disk have markedly increased singulation performance when used in place of celled-disk, both have resulted in a system that requires very tedious adjustments by the planter operator in order to achieve optimum performance. Furthermore, the design of this meter and the nature of disks to warp over time has resulted in difficulty in keeping the double eliminator in proper alignment with the disk.
Other vacuum seed meters such as disclosed in U.S. Pat. No. 3,990,606 to Gugenhan have relied upon the flat disk with apertures and a seed stripping “singulator.” These designs have provided for more repeatable and operator-friendly adjustments but the need still remains for adjustment. The meter disclosed in U.S. Pat. No. 5,842,428 to Stufflebeam et al. utilizes a flat disk and three spring loaded singulating spools that compensate for tolerances in one direction, but the spools do not compensate for radial translation of the disk.
Accordingly, there remains a need for a seed singulator that can be used with different types of meters and different types of seed disks, but which can deliver very high singulation accuracy while requiring minimal adjustments for seed type or manufacturing tolerances and wherein the singulation accuracy is not adversely effected by axial and radial translations of the disk.